86 lines
2.8 KiB
C++
86 lines
2.8 KiB
C++
#ifndef POLYLINECOMPRESSOR_H_
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#define POLYLINECOMPRESSOR_H_
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#include "util/coordinate.hpp"
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#include <algorithm>
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#include <boost/assert.hpp>
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#include <string>
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#include <vector>
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namespace osrm
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{
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namespace engine
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{
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namespace detail
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{
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std::string encode(std::vector<int> &numbers);
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std::int32_t decode_polyline_integer(std::string::const_iterator &first, std::string::const_iterator last);
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}
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using CoordVectorForwardIter = std::vector<util::Coordinate>::const_iterator;
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// Encodes geometry into polyline format.
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// See: https://developers.google.com/maps/documentation/utilities/polylinealgorithm
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template <unsigned POLYLINE_PRECISION = 100000>
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std::string encodePolyline(CoordVectorForwardIter begin, CoordVectorForwardIter end)
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{
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double coordinate_to_polyline = POLYLINE_PRECISION / COORDINATE_PRECISION;
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auto size = std::distance(begin, end);
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if (size == 0)
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{
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return {};
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}
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std::vector<int> delta_numbers;
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BOOST_ASSERT(size > 0);
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delta_numbers.reserve((size - 1) * 2);
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int current_lat = 0;
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int current_lon = 0;
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std::for_each(
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begin,
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end,
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[&delta_numbers, ¤t_lat, ¤t_lon, coordinate_to_polyline](
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const util::Coordinate loc) {
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const int lat_diff =
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std::round(static_cast<int>(loc.lat) * coordinate_to_polyline) - current_lat;
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const int lon_diff =
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std::round(static_cast<int>(loc.lon) * coordinate_to_polyline) - current_lon;
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delta_numbers.emplace_back(lat_diff);
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delta_numbers.emplace_back(lon_diff);
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current_lat += lat_diff;
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current_lon += lon_diff;
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});
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return detail::encode(delta_numbers);
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}
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// Decodes geometry from polyline format
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// See: https://developers.google.com/maps/documentation/utilities/polylinealgorithm
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template <unsigned POLYLINE_PRECISION = 100000>
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std::vector<util::Coordinate> decodePolyline(const std::string &polyline)
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{
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double polyline_to_coordinate = COORDINATE_PRECISION / POLYLINE_PRECISION ;
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std::vector<util::Coordinate> coordinates;
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std::int32_t latitude = 0, longitude = 0;
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std::string::const_iterator first = polyline.begin();
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const std::string::const_iterator last = polyline.end();
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while (first != last)
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{
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const auto dlat = detail::decode_polyline_integer(first, last);
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const auto dlon = detail::decode_polyline_integer(first, last);
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latitude += dlat;
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longitude += dlon;
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coordinates.emplace_back(
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util::Coordinate{util::FixedLongitude{static_cast<std::int32_t>(longitude*polyline_to_coordinate)},
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util::FixedLatitude{static_cast<std::int32_t>(latitude*polyline_to_coordinate)}});
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}
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return coordinates;
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}
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}
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}
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#endif /* POLYLINECOMPRESSOR_H_ */
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